This application relates generally to systems and methods for obtaining and displaying an X-ray image. In particular, this application relates to systems and methods for generating an X-ray image using a digital flat panel detector constructed using silicon wafers, such as crystalline silicon wafers.
Digital X-ray imaging systems are used to generate digital data in a non-invasive manner and to reconstruct such digital data into useful radiographic images. In current digital X-ray imaging systems, radiation from a source is directed toward a subject or object, typically a patient in a medical diagnostic application, a package or baggage in a security screening application, or a fabricated component in an industrial quality control or inspection application. A portion of the radiation passes through the subject or object and impacts a detector. The scintillator of the detector converts the higher-energy X-ray radiation to lower-energy light photons that are sensed using photo-sensitive components (e.g., photodiodes or other suitable photodetectors) present on a light imager panel. The light imager panel is typically divided into a matrix of discrete picture elements or pixels, and encodes output signals based upon the quantity or intensity of the radiation impacting the scintillator above each pixel region. The signals may then be processed to generate an image that may be displayed for review.
The light imager panel may be based on or formed from a silicon semiconductor substrate. Such a silicon substrate may be provided as crystalline silicon (c-Si), which consists of an ordered silicon matrix (e.g., a well ordered crystal lattice), or amorphous silicon (a-Si), which does not have an ordered matrix (e.g., a random crystal lattice). The random crystal lattice of a-Si allows an electron mobility of <1 cm2/(v·s) while the ordered crystal lattice of c-Si allows an electron mobility of approximately 1,400 cm2/(v·s). Because of the higher electron mobility associated with c-Si, the size of features that can be formed using c-Si can be much smaller than those formed from the a-Si, enabling multiple-gate active pixel sensor (APS) designs for a given pixel size. This is in contrast to conventional a-Si designs, in which the number of pixel features for the same pixel size may be limited (e.g., to two), such as to a photodiode and transistor gate. Indeed, in a c-Si APS design, a charge amplifier and/or other relevant electrical features (e.g., additional transistor and/or capacitors) may be provided in each pixel in addition to the basic photodiode and main TFT. Further, at the level of the light imager panel itself, other features, such as analog to digital conversion circuitry (A/D) and readout scanning circuitry, may be provided, as opposed to using off-panel modules. However, even in a c-Si context, there may be other considerations that might favor providing certain such functionality off of the light imager panel.
Light imager panels based on c-Si technology, such as those employing complementary metal-oxide-semiconductors (CMOS) formed from c-Si, may be costly to fabricate for a variety of factors. For example, depending on the size and shape of the light imager panel to be fabricated, multiple c-Si wafers may be needed to fabricate pieces of the panel, which may be tiled to form the overall panel. Likewise, the fabrication time (e.g., the number of masks applied and/or processing steps performed) is proportional to fabrication costs. Similarly, the yield of the fabricated wafers and/or of the cutting and tiling processes may limit the cost improvements that are possible. The present approaches address one or more of these factors.